El Salvador's Santa Ana volcano is swathed in red, but that's not lava.

Known as Ilamatepec in El Salvador, the Santa Ana volcano erupted on Oct. 1, 2005, killing two coffee pickers forcing thousands of nearby residents to evacuate. The eruption was Santa Ana’s first since 1904 – though it has been active since June 2004 – and reportedly spat out hot ash and rocks careening down the volcano’s side, according to media reports.

Santa Ana, the large, flat-topped mound on the left, appears here in a false-color archive image taken by NASA’s Terra satellite well before the recent eruption. Terra’s Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) shows vegetation as red in this image, though a tiny blue spot inside Santa Ana’s innermost crater hints at a crater lake.

Behind the Santa Ana volcano – which is the highest point in El Salvador at 7,812 feet (2,381 meters) – is a lake that fills the Coatepeque Caldera. Formed from the collapse of a series of volcanoes between 57,000 and 72,000 years ago, the caldera has no documented history of eruptions.

The bare, naked cone rising in the foreground is Izalco, a rather recent – geologically speaking – volcano which rose in 1770 and erupted frequently until about 1966. Izalco is covered in black, hardened lava flows, not vegetation. The city of Santa Ana appears in the upper left of this image.

-- SPACE.com Staff

Credit: R. Simmon/T. Gubbels/Asad Ullah/SSAI/ NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.